Many arrays of storage devices deployed in storage area network (“SAN”) environments have built-in redundancy and load balancing capabilities achieved by using a dual controller model. In many cases such storage devices can include at least one array of disks, which can be classified as a redundant array of independent disks (“RAID”). Under such dual controller model arrangements, where the controllers are often referred to as High Availability (“HA”) pairs, individual controllers can be assigned to operate system nodes as primary controllers or “owners” of various volumes or groups of storage devices, with each such group having its own logical unit number (“LUN”). These controllers can also take over volumes of storage devices from their alternate or paired controllers in case of failures. A system host is often aware of both the preferred and the available secondary paths to a LUN, sometimes even acting as the agent forcing the failovers.
Unfortunately, the traditional use of HA pairs to control a given RAID does not tend to provide high levels of redundancy and load balancing across the greater system or network outside of a given HA pair and RAID. That is, while each given storage device array and controlling HA pair may have high levels of redundancy and load balancing therewithin based upon the inherent nature and design of such a subsystem, an overall network containing many such HA pair and storage array subsystems typically does not enjoy such levels of redundancy and load balancing thereacross. This can be an issue where such attributes are desirable over increasingly large data networks. In addition, there is often little to no recourse when an entire array subsystem (i.e., both controllers in an HA pair) goes down within an overall larger network. As such, the ability to have constant access to and even disaster recovery of certain high priority data files across a large data network of many HA pair subsystems may also be desirable in some instances.
Although many network storage systems, devices and methods have generally worked well in the past, there is always a desire for improvement. In particular, what is desired are network storage systems and methods that are able to provide high levels of redundancy and load balancing across individual array subsystems, particularly with respect to high priority data that might otherwise be unavailable when an entire array subsystem fails.